A multi-track recorder for recording audio signals on a plurality of tracks is conventionally known. By means of a multi-track recorder, it is possible to record, for example, a rhythm guitar part on track 1 and a lead guitar part on track 2 using electric guitars, and to further record a vocal part on track 3 using an integrated microphone, and then mix down these parts to generate and record a stereo signal.
JP 2011-530843 A includes disclosure concerning an automatic mastering function of a multi-channel sound system. JP 2011-530843 A describes adjusting channel faders to a uniform value, limiting at least two channels to a uniform output level, limiting each of the other channels to a decibel output level value lower than the uniform output level value of the two channels, and further adjusting a parameter value of at least one of the channel fader, threshold, release, and output level, to thereby carry out further compression and/or limiting of the encoded channels.
In a multi-track recorder, mixdown is normally performed at as high a level as possible without generating distortion, and subsequently a mastering process is performed to complete recording. The mastering process includes executing sound quality correction (equalizer processing), processing for increasing sound pressure (compression processing), and processing for adjusting to a designated level (normalization). Without a certain degree of knowledge and experience, it is difficult for one to obtain desired results from the mastering process. In particular, in the compression processing for increasing sound pressure, threshold and ratio adjustments are relatively difficult. For this reason, there has been proposed a configuration in which several presets are provided for each type of music and a user selects a desired preset from among these presets. However, such a configuration is disadvantageous in that presets may not be effective when the mixdown is not carried out at an appropriate recording level.
FIGS. 5A and 5B schematically show compression processing in the mastering process. FIG. 5A illustrates compression (compressor) processing performed when the mixdown is carried out at an appropriate level. In the figures, 0 dBFS is the target level that serves as a reference, and TH is the threshold value for the compression processing. Compression processing is processing in which parts of a signal having a level exceeding the threshold value are compressed by a predetermined ratio while other parts of the signal having a level at or below the threshold value are maintained. Accordingly, when the mixdown is carried out at an appropriate level and the level reaches the threshold value TH as shown in FIG. 5A, the compression processing is meaningful.
On the other hand, FIG. 5B illustrates compression processing performed when the mixdown is carried out at an inappropriate level that is too low. Although decreasing of the mixdown level can be effective in consideration of preventing distortion due to an overly high level, when the level is too low, the level does not reach the threshold value TH such that compression is not executed at all, rendering the compression processing meaningless. This situation can occur similarly when presets are provided. When the mixdown level is lower than the threshold value TH of a selected preset, the compression processing does not function substantially.